(1) Field of the Invention
The present invention relates to a communication control method, a communication control apparatus and a switching system, and more particularly, the invention is concerned with a frame reception control function in a high-multiplexing communication control apparatus and the switching system, by way of example.
(2) Description of the Related Art
As is reported, for example, in "Timer Processing Method For High-Multiplexing Communication Control LSI" in IEICE (the Institute of Electronics, Information and Communication Engineers) SPRING CONVENTION B-469, a communication control apparatus for performing frame communication in accordance with communication protocols such as HDLC, etc. has been highly multiplexed in recent years such that the number of connections capable of being processed amounts to several thousands. As one of the technical problems to be dealt with in such a high-multiplexing communication control apparatus, there may be mentioned a problem which concerns scheduling of objects subjected to processing.
Heretofore, in a high-multiplexing communication control apparatus, it is known that with a view to making it possible to process the frames received via a plurality of connections, processing driving or activating events are issued in correspondence with the received frames stored in a receiving buffer and registered sequentially in a queue (hereinafter referred to as the event queue) so that the processing unit can take out from the event queue the events sequentially, starting from the leading one, to thereby read out a received frame corresponding to the event from the receiving buffer for processing the received frame.
In this conjunction, it is noted that in the case of a high-multiplexing communication control apparatus designed for processing received frames by making use of the event queue, the event issued upon every reception of the frame is unconditionally registered in the event queue. As a consequence, when a large number of frames are sent out concentratively during a given period by a particular user or terminal equipment, the memory capacity of the event queue is unduly consumed by the plural events issued by that particular user, incurring an unwanted situation that the events for the other users are abandoned because of a shortage in the memory capacity of the event queue. In that case, a system resource such as the function of the processor connected to the communication control apparatus and the like will exclusively be allocated to the processing of the received frames from the particular user, whereby a restriction or limitation is imposed on the service for the other users, giving rise to a problem.
By way of example, the signalling unit of a switching system which is one species of the communication control apparatuses receives a signal frame for controlling a call from a calling party terminal in precedence to setting up a data connection between the terminals. In that case, when a particular terminal issues at a high frequency a control signal for call set-up/disconnection because of occurrence of failure in the terminal or erroneous manipulation thereof by the user, an excessively large number of signal frames will concentratively arrive at the signal processing unit from the particular terminal equipment, which will result in the call control processor unit repeating the set-up/disconnection for the particular connection in vain, involving a problem that the processing for the connections for the other users is thereby delayed.